The dynamic interactions between varieties of biologically active substances regulate various physiological functions, and diseases are caused in an unusual situation when these interactions occur improperly or the interaction between molecules which should not interact each other occurs. In general, two proteins having complementary structure interact and bioactive compounds interact specific parts of tertiary structure of the proteins. These bioactive compounds may be therapeutic candidates for diagnosing, preventing, treating or alleviating diseases involved in the proteins by modulating the function of the target proteins. Studies on screening the disease targets or therapeutics for the disease have been sustained by analyzing the interaction between these proteins and the interactions between proteins and small-molecule compounds.
For example, various techniques such as phage display (Sche et al., Chem. Biol., 6: 707, 1999), yeast two/three-hybrid analysis (Licitra et al., Proc. Natl. Acad. Sci. USA 93: 12817, 1996), and parallel analysis of yeast strain having deletions heterologous (Zheng et al., Chem. Biol., 11: 609, 2004) have been suggested. However, these techniques have problems, such as high background, false positive and low sensitivity of the reaction and with in vitro experiment or reactions using non-mammalian cells make it hard to convince the experimental result.
In addition, inducing a deletion or a mutation of the gene encoding a protein or treating specific inhibitor for the protein to the cell or the subject expressing the protein are used to observe the physiochemical changes in the cell or the subject.
Among these methods, U.S. Pat. No. 5,270,163 discloses a method for screening specific biomolecules that bind specifically to single-stranded oligonucleotides, the so-called aptamer. Lunder et al. discloses a method of screening target-binding motif using phage display (Lunder et al., Appl. Biochem. Biotechnol., 127 (2): 125-131, 2005). U.S. Patent Publication No. 2010-0143371 discloses a method for inhibiting the function of the proteins in the cell using an intrabody which is a variable domain of kappa chain of human antibodies that specifically bind to intracellular proteins.